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Polydactyly and Syndactyly

What is polydactyly?

Polydactyly, a congenital abnormality, is the presence of more than the normal number of fingers or toes. the condition is usually inherited as an autosomal dominant characteristic and can usually be corected by surgery. If recommended, the surgery is usually done while the child is about 1 year of age. Also called polydactylia, polydactylism or hyperdactyly. Polydactyly can vary from an unnoticeable rudimentary finger or toe to fully developed extra digits. Polydactyly and syndactyly (fusion of the fingers or toes) can occur simultaneously when extra digits are fused. This condition is known as polysyndactyly.

What is syndactyly?

Syndactyly is the webbing or fusing together of two or more fingers or toes. It varies in degree of severity from incomplete webbing of the skin of two digits to complete union of digits and fusion of the bones and nails. the fusion can be simple with the digits connected only by skin, or it can be complicated with shared bones, nerves, vessels, or nials. Also called syndactylia or syndactylism.

What are the causes and symptoms?

Polydactyly is due to errors in the process of fetal development. For example, syndactyly results from the failure of the programmed cell death that normally occurs between digits. Most often these errors are due to genetic defects. Polydactyly and syndactyly can both occur by themselves as isolated conditions or in conjunction with other symptoms as one aspect of a multi-symptom disease. There are several forms of isolated syndactyly and several forms of isolated polydactyly; each of these, where the genetics is understood, is caused by an autosomal dominant gene. This means that since the gene is autosomal (not sex-linked), males and females are equally likely to inherit the trait. This also means that since the gene is dominant, children who have only one parent with the trait have a 50 percent chance of inheriting it. However, people in the same family carrying the same gene can have different degrees of polydactyly or syndactyly.

Polydactyly and syndactyly are also possible outcomes of a large number of rare inherited and developmental disorders. One or both of them can be present in more than 100 different disorders where they are minor features compared to other characteristics of these diseases. In some isolated cases of polydactyly or syndactyly, it is not possible to determine the cause. Some of these cases might nevertheless be due to genetic defects; sometimes there is too little information to demonstrate a genetic cause. Some cases might be due external factors like exposure to toxins or womb anomalies.


Polydactyly and syndactyly can be diagnosed by external observation, X-ray, or fetal sonogram.


Polydactyly can be corrected by surgical removal of the extra digit or partial digit. Syndactyly can also be corrected surgically, almost always with the addition of a skin graft from the groin.


The prognosis for isolated polydactyly and syndactyly is excellent. When polydactyly or syndactyly are part of a syndrome or group of medical conditions, the prognosis depends on the syndrome. Some of these syndromes can be quite serious.


This information has been designed as a comprehensive and quick reference guide written by our health care reviewers.  The health information written by our authors is intended to be a supplement to the care provided by your physician.  It is not intended nor implied to be a substitute for professional medical advice. 


Penn State Milton S. Hershey Medical Center ©2004
This page was last updated on October 31, 2006
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